Follistatin-344: research
Human gene-therapy findings do not establish a dose for follistatin-344 protein vials.
Also called: FS344, FST344, FS-344, Follistatin 344.
Myostatin pathway · Myostatin- and activin-binding protein precursor.
Gene-vector administration is separate from direct protein exposure. Registrations do not establish results. A protein-injection evidence level is not established here.
Studies
- Becker gene transfer, six adults. open-label, n=6, Six men with Becker muscular dystrophy. Four of six improved walking distance after gene transfer; no randomized control. (source)
- Myositis gene transfer, six adults. open-label, n=14, Six men with sporadic inclusion body myositis, plus eight matched untreated controls. Walking gains were reported, but exercise, steroids and unequal follow-up limit attribution. (source)
- Registry and early myositis cohort. open-label, n=15, 15 enrolled across Becker muscular dystrophy and inclusion body myositis cohorts. Registry includes three early low-dose myositis patients beyond the two six-person publications. (source)
- Duchenne gene transfer, phase 1/2. open-label, n=3, Three boys with Duchenne muscular dystrophy; six originally planned. No dose-limiting toxicity was reported; the registry does not show improved walking at two years. (source)
- Plasmid gene delivery, unreviewed report. open-label, n=43, 43 adults aged 23–88 years, both sexes. An uncontrolled manuscript reports small body-composition changes and increased LDL cholesterol. (source)
- Klotho plus follistatin plasmids. open-label, n=14, 14 healthy adult volunteers. Completed registration has no posted results or verified clinical benefit. (source)
- CALM-AF-AI: phase 1/2 gene transfer. open-label, Adults aged 35–75 with age-related muscle decline; estimated enrollment 12. Recruiting gene-therapy study; no results as of the review date. (source)
- Retinal fluid after reported 1 mg injections. case-series, n=11, 11 male bodybuilding athletes; mean age 36.8 ±8.1 years. Retinal fluid leakage followed reported whole-vial injections; incidence and causation remain uncertain. (source)
- Primate gene transfer. animal, n=6, Six cynomolgus macaques, plus untreated comparison animals. AAV gene delivery enlarged quadriceps muscles; this cannot validate human protein injections. (source)
- Testing 17 online protein products. in-vitro, n=17, 17 products sold as follistatin-344. Only 9/17 contained follistatin; identified protein carried manufacturing tags and oligomers. (source)
Follistatin-344 dosage
Typical reported dose: 100 mcg once a day
- Reported 100 mcg daily course: 100 mcg daily daily, under the skin. Reported by users, rare report. Studied in: Adults discussing self-use for muscle growth. (source)
- Same log, intramuscular use: 100 mcg daily after changing route daily, into muscle. Reported by users, rare report. Studied in: Adults discussing self-use for muscle growth. (source)
- Circulating daily range: 100–200 mcg daily for 10–30 days daily, under the skin. Reported by users, rare report. Studied in: Adults discussing self-use for muscle growth. (source)
- Circulating training-day schedule: 50 mcg on training days on training days only, into muscle. Reported by users, rare report. Studied in: Adults discussing self-use for muscle growth. (source)
- Whole-vial exposure in eye cases: Adverse-event exposure in a retrospective eye-clinic case series: complete 1 mg vials injected subcutaneously; not an established treatment regimen. one reported injection; repeats varied, under the skin. Reported by users, rare report. Studied in: Eleven male bodybuilding athletes presenting with central serous chorioretinopathy after self-directed injections. (source)
These are doses reported in labels, trials or user reports, not a personal plan. Check the source behind each one.
Follistatin-344 side effects and risks
Reported side effects
- Retinal fluid leakage and blurred vision: 11 selected eye cases after reported 1 mg injections; user wide incidence unknown., serious. Stop injections and seek urgent eye assessment for new blur, distortion or a dark spot. (source)
- Injection pain, swelling and fever-like symptoms: Reported in one self use log; no reliable rate., moderate. Stop further exposure and seek assessment for marked swelling, persistent fever or worsening pain. (source)
- Immune reactions or contaminants: Human rates are unknown; market testing found wrong proteins and manufacturing tags., serious. Breathing trouble or facial swelling needs emergency care. (source)
- Reproductive-hormone effects: Activin binding creates a mechanistic concern; human protein injection risk is unknown., moderate. Review fertility plans and menstrual or sexual changes with a clinician. (source)
- Raised LDL after plasmid gene delivery: Unreviewed 43 person manuscript reports mean LDL +11.6 mg/dL at three months., moderate. This gene-therapy finding cannot be assigned to protein-vial use. (source)
Stop and get help if
- New blurred or distorted vision, or a central dark spot: Stop injections and get urgent eye care today.
- Breathing trouble, fainting, or swelling of the face or tongue: Call emergency services now; stop further exposure.
- Fever with a hot, expanding injection-site swelling or severe pain: Stop injections and get urgent medical assessment.
Who should avoid it
- pregnant: No pregnancy safety data for protein injections; gene-therapy trials exclude pregnancy.
- breastfeeding: No infant-exposure or breastfeeding safety data; excluded in the current AAV trial.
- tryingToConceive: Activin affects reproductive signaling; safe fertility exposure and washout are unknown.
- under18: Adult self-use protocols exclude minors; three pediatric gene-transfer cases do not establish protein-injection safety.
- activeCancer: Current gene-therapy trial excludes active or recent cancer. Protein effects on cancer growth are unresolved.
- cancerHistory: Recent cancer is excluded from current gene-therapy research; long-term recurrence risk is unknown.
- other: Reported high-dose use is linked to retinal fluid leakage; avoid further exposure with active or prior disease.
- liverDisease: Human protein dosing in liver disease is unstudied; gene-transfer studies monitor liver tests.
- kidneyDisease: Dose changes in kidney disease are unknown; gene-transfer studies monitor kidney function.
- immunosuppressed: Product sterility and immune risks are unresolved; AAV studies require specialized immune screening.
- surgeryPlanned: No perioperative safety or validated washout for protein injections was found.
- testedAthlete: Follistatin is prohibited at all times under WADA S4.3; gene transfer may also fall under M3.
Interactions
- Corticosteroids: Both exposures are linked to retinal fluid leakage. Additive risk is a precaution; no combination trial exists.
- Other myostatin or activin blockers: Overlapping growth-signal blockade has unknown combined risks. No human trial supports stacking these products.
- Growth hormone and IGF products: Discussed together for muscle gain; no human trial establishes safety or added benefit with injected follistatin.
Product quality risks
- Only 9/17 tested products contained follistatin; all nine had His-tags and many protein oligomers.
- Other tested products contained growth-related peptides such as MGF or GHRP-2.
- The label does not establish identity, amount, biological activity, sterility or endotoxin safety.
How Follistatin-344 works
Follistatin binds myostatin and activin, signals that normally limit muscle growth. FS344 is a gene-encoded precursor that becomes circulating FS315 after processing. Gene therapy makes cells produce protein; a vial injection has different exposure and risks.
- Myostatin / GDF-8: Binding prevents a signal that limits muscle growth.
- Activins: Binding also affects signals involved in reproduction and other tissues.
Half-life: Human half-life of injected follistatin-344 protein is unknown.
Gaps: No controlled dose-finding, efficacy or pharmacokinetic trial of community follistatin-344 protein injections was found. Gene therapy, plasmid DNA and recombinant protein have different dose units, exposure and risks. Human protein-injection pregnancy, breastfeeding, fertility, immune and long-term cancer risks remain unknown. Three early unilateral myositis patients lack a separate full outcome report; registry and publication cohort wording differs. Myositis walking benefits are disputed and confounded by prednisone, exercise and unequal follow-up. The 43-person plasmid manuscript is uncontrolled and unreviewed; no registry results are posted. The 14-person combination trial and recruiting AAV9 trial have no posted results. No validated protein-vial reconstitution, shelf life or safe repeat-cycle interval was found. Community prevalence is unmeasured; guide circulation is not proof of common completed use. No compound-specific poison-center series or current representative market survey was located. The evidence level includes related gene-therapy studies and observed protein exposure; it does not indicate a validated protein protocol.
Related to Follistatin-344
- ACE-031: An experimental muscle-growth protein whose Duchenne program stopped over bleeding concerns.
- Ipamorelin: An experimental peptide that triggers growth hormone release.
- IGF-1 LR3: An unapproved growth signal with no human trials found.
- PEG-MGF: A modified MGF peptide with no human dosing studies and uncertain identity in unregulated vials.
Follistatin-344: the short version
Sources
- 503B Bulk Drug Substances List, FDA · FDA · 2026
- Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act, FDA · FDA · 2026
- Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act, FDA · FDA · 2026
- Cellulitis, NHS · NHS · 2026
- Find product information about medicines, Medicines and Healthcare products Regulatory Agency · MHRA · 2026
- Medicines, European Medicines Agency · European Medicines Agency · 2026
- Pyrogen and Endotoxins Testing: Questions and Answers, FDA · 2026
- The 2026 Prohibited List, World Anti-Doping Agency · WADA · 2026
- Therapeutic Goods (Poisons Standard—October 2026) Instrument 2026, Australian Government · Australian Government · 2026
- Anaphylaxis, NHS · NHS · 2023
- Definition of the Term “Biological Product” Final Regulatory Impact Analysis, FDA · 2020
- Tailor Made Compounding LLC - 594743 - 04/01/2020, FDA · FDA · 2020
- Australian Register of Therapeutic Goods (ARTG), Therapeutic Goods Administration · TGA
- Mixing, Diluting, or Repackaging Biological Products Outside the Scope of an Approved Biologics License Application Guidance for Industry, FDA
- Search criteria - Drug Product Database online query, Health Canada · Health Canada
Sources checked: 2026-10-18.
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